Chapter 10, Problem 22P

Summary Introduction

To determine: The standard time for the operation

Introduction: Time study is the basis that helps set the standard time; it would time a sample of the performance of the worker.

Answer to Problem 22P

Thestandard time is calculated as 10.12 minutes.

Explanation of Solution

Given information:

The allowance factor is given as 10%. The observed time and performance rating for each element is given as follows:

Element	Performance rating	Observation (minutes per cycle)
		1	2	3	4	5
Check mini-bar	100	1.5	1.6	1.4	1.5	1.5
Make one bed	90	2.3	2.5	2.1	2.2	2.4
Vacuum floor	120	1.7	1.9	1.9	1.4	1.6
Clean bath	100	3.5	3.6	3.6	3.6	3.2

Formulae to calculate the standard time:

$\text{Average time}=\frac{\text{Observed times for gift-wrapping}}{n}$

$\text{Normal time}=\text{Average time}\times \text{Performance rating}$

$\text{Standard time}=\frac{\text{Normal time}}{1-\text{Allowance factor}}$

Calculate the standard time:

Element	Performance rating	Observation (minutes per cycle)					Average time	Normal time
		1	2	3	4	5
Check mini-bar	100%	1.5	1.6	1.4	1.5	1.5	1.5	1.5
Make one bed	90%	2.3	2.5	2.1	2.2	2.4	2.3	2.07
Vacuum floor	120%	1.7	1.9	1.9	1.4	1.6	1.7	2.04
Clean bath	100%	3.5	3.6	3.6	3.6	3.2	3.5	3.5
Total								9.11

Excel worksheet:

Calculate the average time to check mini-bar:

The average time is calculated by taking an average of the observation given, which is a summation of 1.5, 1.6, 1.4, 1.5, and 1.5 and dividing the result by 5. Hence, the average is 1.5 minutes.

$\begin{array}{c}\text{Average time}=\frac{\text{Observation}}{n}\\ =\frac{1.5+1.6+1.4+1.5+1.5}{5}\\ =\frac{7.5}{5}\\ =1.5\text{ minutes}\end{array}$

Calculate the average time to make one bed:

The average time is calculated by taking an average of the observation given, which is summation of 2.3, 2.5, 2.1, 2.2, and 2.4 and dividing the result by 5. Hence, the average is 2.3 minutes.

$\begin{array}{c}\text{Average time}=\frac{\text{Observation}}{n}\\ =\frac{2.3+2.5+2.1+2.2+2.4}{5}\\ =\frac{11.5}{5}\\ =2.3\text{ minutes}\end{array}$

Calculate the average time to vacuum floor:

The average time is calculated by taking an average of the observation given, which is summation of 1.7, 1.9, 1.9, 1.4, and 1.6 and dividing the result by 5. Hence, the average is 1.7 minutes.

$\begin{array}{c}\text{Average time}=\frac{\text{Observation}}{n}\\ =\frac{1.7+1.9+1.9+1.4+1.6}{5}\\ =\frac{8.5}{5}\\ =1.7\text{ minutes}\end{array}$

Calculate the average time to clean bath:

The normal average time is calculated by taking an average of the observation given, which is summation of 3.5, 3.6, 3.6, 3.6, and 3.2 and dividing the result by 5. Hence, the average is 3.5 minutes.

$\begin{array}{c}\text{Average time}=\frac{\text{Observation}}{n}\\ =\frac{3.5+3.6+3.6+3.6+3.2}{5}\\ =\frac{17.5}{5}\\ =3.5\text{ minutes}\end{array}$

Calculate the normal time to check mini-bar:

The normal time is calculated by multiplying average time and performance rating. The average time is given as 1.5 minutes, and performance rating is given as 100%. Hence, the normal time is 1.5 minutes.

$\begin{array}{c}\text{Normal time}=\text{Average time}\times \text{Performance rating}\\ =1.5\times 100\%\\ =1.5\times 1\\ =1.5\text{ minutes}\end{array}$

Calculate the normal time to make one bed:

The normal time is calculated by multiplying average time and performance rating. The average time is given as 2.3 minutes, and performance rating is given as 90%. Hence, the normal time is 2.07 minutes.

$\begin{array}{c}\text{Normal time}=\text{Average time}\times \text{Performance rating}\\ =2.3\times 90\%\\ =2.3\times 0.9\\ =2.07\text{ minutes}\end{array}$

Calculate the normal time to vacuum floor:

The normal time is calculated by multiplying average time and performance rating. The average time is given as 1.7 minutes, and performance rating is given as 120%. Hence, the normal time is 2.04 minutes.

$\begin{array}{c}\text{Normal time}=\text{Average time}\times \text{Performance rating}\\ =1.7\times 120\%\\ =1.7\times 1.2\\ =2.04\text{ minutes}\end{array}$

Calculate the normal time to clean bath:

The normal time is calculated by multiplying average time and performance rating. The average time is given as 3.5 minutes, and performance rating is given as 100%. Hence, the normal time is 3.5 minutes.

$\begin{array}{c}\text{Normal time}=\text{Average time}\times \text{Performance rating}\\ =3.5\times 100\%\\ =3.5\times 1\\ =3.5\text{ minutes}\end{array}$

Calculate the total normal time:

The normal time is calculate by adding the normal time to check the mini-bar, make one bed, vacuum floor, and clean bath.

$\begin{array}{c}\text{Normal time}=\text{Sum of normal times}\\ =1.5+2.07+2.04+3.5\\ =9.11\text{ minutes}\end{array}$

Hence, the total normal time is 9.11 minutes.

Calculate the standard time:

The standard time is calculated by dividing the normal time with the value attained by subtracting the allowance factor from 1. Normal time is calculated as 9.11 minutes and the allowance factor is calculated as 0.10 or 10%.

$\begin{array}{c}\text{Standard time}=\frac{\text{Normal time}}{1-\text{Allowance factor}}\\ =\frac{9.11\text{ minutes}}{1-0.10}\\ =\frac{9.11\text{ minutes}}{0.9}\\ =10.12\text{ minutes}\end{array}$

Hence, the standard time is 10.12 minutes.